The goal of this proposal is to develop a new detector technology for digital x-ray imaging based on Hgl2 polycrystalline films coupled to large area fiat panel amorphous silicon (a-Si:H) thin-film transistor (TFT)addressed readout arrays. This novel Imaging detector when optimized will provide order of magnitude improvements in sensitivity to x-rays and superior spatial resolution compared to detectors utilizing scintillating phosphors coupled to a-Si:H readout arrays. The increased sensitivity of the detector will allow for a ten-old reduction in radiation dose to a patient for an equivalent quality image. The enhancement of the spatial resolution will have a direct impact on the quality of the image1 which has paramount importance in many medical diagnostic procedures such as mammography. In addition, digital capabilities will allow for convenient film-less image acquisition, retrieval, and storage. Digital image processing, computer-assisted diagnosis, and the ability to provide real time images have distinct advantages in many medical diagnostics. During Phase I of this proposal we will develop techniques for highly controlled growth of polycrystalline Hgl2 films In terms of their thickness, sizes of the polycrystalline gains, uniformity of layers and good electrical properties. The film depositions will initially be done with samples ranging from 1" to 2" square. The thickness of the samples will be grown from 1OO-5O0 microm. The developed growth methods will be easily scalable to much larger areas. The process will be optimized for low production cost. In Phase II we will finalize the Hgl2 film development and construct large area (about 10" x10") x-ray imaging detector using a commercial fiat panel a-Si:H readout This new x-ray imager will then be characterized for sensitivity, spatial resolution and imaging capabilities in our laboratory and at UCLA School of Medicine with the use of slits and phantoms. PROPOSED COMMERCIAL APPLICATION: There is a strong interest in application of digital radiographic detectors for medical diagnostic applications, non-destructive evaluation of materials, x-ray diffraction of biological and other material samples, and astronomical observations. Conservative estimates are that in the medical area alone there are over 800 x-ray images produced per 1000 population per year. The proposed detectors will be highly attractive to this enormous commercial market segment due to the order of magnitude performance improvements that they will offer.